Etching is a process that can texturize the surface of a silicon wafer. Silicon wafers having texturized surfaces are useful as solar cells as less incident light is reflected off the wafer surface. As a result more light energy is absorbed by the silicon, making the silicon wafer more efficient in energy capture. The pattern of the texture directly affects the reflectance of the solar cell.
Although the chemical reaction is well known, the anisotropic etching of silicon is a complex process. This is particularly true in the solar industry where a large mass of silicon is typically introduced into an etch bath. The etch by-products (silicates) affect the balance of the etching species. If adequate compensation is not made for these by-products, a significant drop in etch rate and an increase in contamination levels is typically noticed. Because of this contamination, production lines suffer from unpredictable wafer characteristics and lower cell performance. Previous attempts to control the etch rate included using refractory sensors for measuring the content of particulates in the etchant solution, which was used to calculate the progress of an etching reaction. Such methods are limited by the type of refractory sensor that may be effectively used to measure particulate amounts.
Thus, a need exists for a system and/or method that can effectively maintain consistent etch rate at a desired level over an entire bath life using measurement techniques other than refractory sensors. Furthermore, a need exists for a system and/or method that, produces consistent textorization patterns on the silicon wafers over the entire bath life.